This application relates to a transformer, and more specifically, to a transformer used in an electronics module of an electric vehicle.
For an electric vehicle to be commercially viable, its cost and performance should be competitive with that of its gasoline-powered counterparts. Typically, the vehicle's propulsion system and battery are the main factors which contribute to the vehicle's cost and performance competitiveness.
Generally, to achieve commercial acceptance, an electric vehicle propulsion system should provide the following features: (1) vehicle performance equivalent to typical gasoline-powered propulsion systems; (2) smooth control of vehicle propulsion; (3) regenerative braking; (4) high efficiency; (5) low cost; (6) self-cooling; (7) electromagnetic interference (EMI) containment; (8) fault detection and self-protection; (9) self-test and diagnostics capability; (10) control and status interfaces with external systems; (11) safe operation and maintenance; (12) flexible battery charging capability; and (13) auxiliary 12 volt power from the main battery. In prior practice, however, electric vehicle propulsion system design consisted largely of matching a motor and controller with a set of vehicle performance goals, such that performance was often sacrificed to permit a practical motor and controller design. Further, little attention was given to the foregoing features that enhance commercial acceptance.
For example, a typical conventional electric vehicle propulsion system consisted of a DC motor, a chopper-type motor controller, an independent battery charger, and a distributed set of controls and status indicators. Vehicle performance was generally inadequate for highway driving, acceleration was uneven, and manual gear-changes were required. In addition, regenerative braking was either not available or, at best, available only at high motor speeds. Also, each of the system components had its own cooling system that used forced air or a combination of forced air and liquid cooling. Moreover, the issues of volume production cost, EMI, fault detection, maintenance, control and status interfaces, and safety were generally not addressed in a comprehensive manner.
Electric vehicles often include an electronics module, such as a DC/DC converter, that includes a transformer. Transformers of a type suitable for use in electronic vehicles usually include a "core" and some type of "winding" surrounding the core. Generally, a transformer should be able to dissipate thermal energy from the windings. In addition, the transformer should be easy and inexpensive to manufacture.
Conventional transformers are assembled as a subassembly unit, after which the subassembly unit is added to a larger electronics module. During assembly of a conventional transformer subassembly unit, two E-shaped core members are first placed so that the "legs" of the E's touch and are in alignment. Next a wire "winding" is wound around a center leg of the core members. A steel band is placed around the entire subassembly, either before or after the winding step, to secure the core members together.
Assembling such a transformer subassembly is time consuming. Furthermore, the subassembly must be assembled separately before it can be added to the main electronics module. In addition, it is difficult to perform the winding step because the winding material must be threaded through the legs of the core members.
After assembly, some transformer subassemblies are mounted to a mounting surface by placing the subassembly parallel to the mounting surface and covering both the subassembly and the mounting surface with potting compounds. In other instances, the transformers subassembly is bolted to the mounting surface. Conventional transformer subassembly units may be surrounded by steel bands or some other means of holding the subassembly together.